Tire pressure alarm



Patented Feb. 1, 1949 UNITED STATES PATENT OFFKIE 2,460,315 TIRE PRESSURE ALARM William Torrance, Calgary, Alberta, Canada Application July 14, 1947, Serial No. 760,735

its construction the device may be used on various sized tires with the use of suitable adapter fittings and may be readily adjusted for operation at selected tire pressures.

Another object of this invention is to provide a tire alarm of this kind which is formed of relatively few moving parts to provide a highly efficient alarm, and so constructed and arranged that it may be maintained and adjusted with the minimum of labor and time.

A further object of this invention is to provide an alarm of this kind having a spring-pressed firing pin which is heldin place by a pair of retaining lugs and in which the retaining lugs are moved to pin rel-easing position by the sliding L movement of a pressure responsive piston c-onnected to the tire.

Still another object of this invention is to provide a reliable device of this kind which may be readily manufactured and assembled at a low 'cost and with a minimum expenditure of time and labor and which is easily installed and operated.

With the above and other objects in view, my invention consists in the arrangement, combination and details of construction disclosed in the drawings and specification, and then more particularly pointed out in the appended claims.

In the drawings,

Figure 1 is a longitudinal section taken through a tire pressure alarm constructed according to an embodiment of this invention,

Figure 2 is a transverse section, partly broken away, taken on the line 2-2 of Figure 1,

Figure 3 is a top plan view, partly broken away and partly in section, showing the relationship of the slidably connected piston shafts and the retaining pin,

Figure 4 is a side elevation, partly broken away, of the sliding shafts showing the retaining pin in the released position; and

Figure 5 is a bottom plan View of the retaining pin removed from the assembly.

Referring to the drawing, the numeral l0 designates generally a tire pressure alarm which is constructed for firing a .cartridge when the pres- 4 Claims. (Cl. 116-34) below a predetermined value.

sure in the truck or automobile tire has fallen The tire pressure alarm I0 is formed with an enlongated tubular housing or body H which is adapted to be connected at one end to the stem of a tube or tire so that the air pressure in the tube may be trans--v lated into the housing or body I i.

The body i l is open at both ends and provided with screw plugs l2 and M for closing the ends of the tube. An inlet port I5 is provided at one end of the housing H adjacent the plug [2 to which the stem it of thetube is adapted to be attached. The opening is provided through a radially extended boss H on the body H. A boss i8 is provided on the opposite side of the end of the housing i I diametrically opposite from the inlet port l5. opening 19 therethrough.

A valve connector C is adapted to be connected to the boss I8 for releasing air from the tire without removing the alarm from the tire. The opposite end of the body H is closed with a nut M which is formed with a bore 20 therethrough having an enlarged recess 2! at the inner end thereof in which a cartridge 22 is adapted to be frictionally engaged. The nut !4 may be readily removed for changing the cartridge after it has been shot.

An annular bead or rib 24 is provided internally of the body H midway the length thereof. A piston 25 is slidablydisposed in the body ll between the rib 24 and the inlet end of the housing. The piston 25 is threadably engaged about the reduced diameter end 26 of a tubular shaft 21. The enlarged end of the tubular shaft 21 is slidably engaged orjournaled in the rib 24 and is limited in its sliding motion in one direction by a slightly enlarged rib 23 about the shaft 21 which is adapted to abuttingly engage the inner end of the rib 24. V

The piston 25 is preferably cup-shaped, as shown in Figure 1, and the piston 25 is secured on the shaft 26 by a nut 29. A spring 30 is engaged in the housing I! about the shaft 2'! and abuts at one end the rib 24 and at the other end the outer surface of a spacer 3! between the inner end of the spring 30 and the piston cup 25. The piston 25 is adapted to be moved outwardly toward the rib 24 by the air pressure entering through the opening 15. The spring 30 constantly urges the piston 25 inwardly against the air pressure and the tension of the spring 38 may be adjusted by moving the location of the nut 29 and piston'25 along the length of the reduced end 26 of the shaft 21. In this manner the tire pressure alarm The boss i8 is formed with an I may be adjusted for different tire pressures and for various sized tires.

A second piston 32 is slidably disposed in the other end of the body ll adjacent the cartridge 22. A firing pin 34 is fixed to or carried by the outer end of the piston 32 and is adapted to detonate the cartridge 22 when the piston is sharply forced towards that end. A rod 35 is connected to the inner end of the piston 32 and is adapted to slidingly engage within the hollow end of the tubular shaft 21.

A spring 36 engaging at its inner end against the outer side of the rib 24 engages the inner side of the piston 32 for constantly biasing-the piston to the cartridge detonating position.

For holding the piston 32 and firing pin 34 in the cocked position a pair of oppositely disposed retaining pins 3'! are slidably carried in the body I l and extend through the rib 24. Tubular bosses 3B are provided on opposite sides of the housing H outwardly of the rib 24 within which the pins 37 are slidable. The pins 31 are; cylindrical throughout the greater portion of their length and formed at the outer end thereof with a counterbore 33. A spring 40 is disposed in the counterbore 39 and abuts at its upper end the inner end of an adjusting screw 4!. The screw M is threadably engaged in the boss 38 for adjusting the tension on the retaining pins 37.

The retaining pins 31 in order to operatively engage the rod 35 on which the piston 32 is connected must extend through the tubular shaft 21. To provide for this movement the shaft 27 is formed with longitudinally extending slots 42 on opposite sides thereof at its outer end. A downwardly extending rectangular lug 44 is fixed to or formed on the lower end of the retaining pin 31. The lug 44 is adapted to freely engage through the slots 42 of the shaft 2! and engage retainingly in an annular groove 45 formed on the shaft 35 intermediate its length.

When the ing 44 is engaged in the groove 45 the piston 32 is held in the cooked position, with the spring 35 exerting a pressure outwardly. For raising the retaining pins 31 from their retaining position, correlated cams are formed on the lower end of the pins 3'! and on the slotted shaft 27.

A downwardly and inwardly inclined surface 46 is formed on the shaft 21 at the inner end of the slot 42. The surface 45 is formed on both sides of the slot and provides a moving cam on the shaft 22. A correlated cam surface 4? is formed on the lower end of the retaining pin 37 at the upper end of the lug 44. The cam surface 41 extends outwardly of the lug 44 and is disposed in an outwardly and upwardly inclined direction.

In the use and operation of the tire pressure alarm l0, when sufficient pressure is in the tire the piston 25 will be moved outwardly against the tension of the spring 3!] until the rib 28 is in engagement with the rib 24. In this position the piston 32 may be pressed inwardly against the tension of the spring 36 until the retaining pins 37 are in engagement with the shaft 35.

The lugs 44 at this time will be engaged inthe annular groove 45 for retaining the piston 32 in this position. The plug l4 may then be'in'stalled on the outer end of the body ll, having a car-'- tridge 22. As the tire pressure decreases below the tension of the spring 353, the piston 25 and the shaft 21 will be moved inwardly. As the shaft 21 moves the cam siu'face 46 will engage the cam surface 47 for raising. the pins 31 against the tension of the springs 40. Upon sufficient movement of the shaft 21 inwardly the lugs 44 will be raised out of the groove 45. At this time the spring 36 will move the piston 32 sharply to the right as viewed in Figure 1, causing the firing pin 34 to detonate the cartridge 22. The sound of the exploding cartridge will indicate to the driver of the truck or automobile that the tire pressure in one of the tires has decreased below a safe point and he may take the necessary precautions.

I do not mean to confine myself to the exact details of construction herein disclosed, but claim all variations falling within the purview of the appended claims.

What I claim is:

1. A tire pressure alarm comprising a tubular body, a piston slidable in one end of said body, a tubular shaft carried by said piston and extending longitudinally of said body, said body formed at said one end with an air inlet opening for attachment to a tire, said shaft formed with a longitudinal slot therethrough at the end opposite from said piston, a spring-pressed retaining pin carried by said body radially thereof and extending through said slot, a second pistori slidable in said body at the other end thereof, a rod on said second piston slidable in said tubular shaft, said rod formed with an annular recess in which said pin is engageable, means supporting a cartridge in said other end of said body, a firing pin on said second piston, spring means biasin pistons toward their respective ends of said housing, and correlated cam means carried by'said shaft and said retaining pin for disengaging said pin from said rod upon sliding of said shaft, whereupon said cartridge may be fired upondecrease of tire pressure.

2. A tire pressure alarm comprising a tubular body, an internal annular rib in said body intermediate the length thereof, a piston slidable in said body on one side of said rib, a tubular shaft onsaid piston journaled in said rib, a spring about said shaft between said rib and said piston; said cylinder formed with an air inlet for admitting air under pressure to press said piston against the spring tension, 21. second piston slidable in said body onthe opposite side ofsaid rib, a rod-on said latter piston slidable in said shaft, a firing pin on said latter piston, a spring about said rod between said latter piston and said rib, means supporting a cartridge in said body for detonation by saidfiring pin, said shaft formed with a longitudinal elongated slot at the end opposite from said piston, said rod formed with a peripheral groove intermediate the length thereof, opposed spring-pressed retaining pins carried by said body engageable through said slot and in said groove for retaining said rod against the spring tension, and correlated cams carried by said shaft and retaining pins for raising said pins from said groove upon a decrease of air pressure against said first piston, whereupon said latter piston and said firing pinare slid sharply toward said cartridge.

3. A tire pressure alarm comprising a tubular body, means removably supporting a cartridge at one end of said body, a pair of oppositely disposed pistons-slidable in said body, spring means biasing said pistons toward the opposite ends of said body, a firing pin on one'of said pistons for detonating said cartridge, said body formed with an air inlet at the other end whereby air pressure may hold the other piston against the springtension, a recessed rod on saidone' pis-' ton, a slotted shaft on said other piston about said rod, spring-pressed radially disposed retaining pins in said body engaging in said recessed rod for restraining said first piston against spring tension, and correlated cam means carried by said shaft and said restrainin pins for releasing said pins from said rod upon a decrease of pressure on said latter piston.

4. A tire pressure alarm comprising a tubular body, means removably supporting a cartridge at one end of said body, a pair of oppositely disposed pistons slidable in said body, spring means biasing said pistons toward opposite ends of said body, a firing pin on one of said pistons for detonating said cartridge, said body formed with an air inlet at the other end whereby air pressure may hold the other piston against the spring tension, a longitudinally slotted tubular shaft on said other piston formed with a cam surface at one end of said slot, a rod on said one piston formed with a peripheral. recess intermediate the length thereof, said rod slidable in said shaft, spring pressed retaining pins radially slidable in said body, each of said pins including a lower cam surface engageable with the cam of said REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Knies May 6, 1913 Michelin Feb. 1, 1921 Harris Feb. 15, 1921 FOREIGN PATENTS Country Date France Sept. 22, 1930 Number Number 

